1. Field of the Invention
This invention relates to a photoelectric conversion device, and particularly to a device for extracting a plurality of space frequency components from an optical image.
2. Description of the Prior Art
Various devices for electrically extracting information related to the specific space frequency component of an optical image and detecting, for example, the focus of an optical system on the basis thereof have been proposed. We already filed, on Nov. 13, 1978, U.S. Application Ser. No. 959,918 (German counterpart P 2848874), now U.S. Pat. No. 4,218,623, covering a device for converting the outputs of the photoelectric element of a photoelectric element array upon which an optical image is projected into vectors having magnitudes corresponding to the magnitudes of said outputs, i.e. absolute values, and phases successively deviated by 2.pi./N each (N is an integer equal to or greater than 2) in the order of arrangement of the photoelectric elements and adding together those vectors to thereby extract specific space frequency component information having, as the space period, the length of N photoelectric elements in the direction of arrangement. However, such a specific space frequency component extracting device is useless when the optical image scarcely contains the specific space frequency component, and it is impossible to detect the focus of the optical system on the basis of the output of this device.
To avoid such a situation, a plurality of space frequency components may be extracted from the optical image. For this purpose, it occurs to mind to use a plurality of photoelectric element arrays or to divide a single photoelectric element array into a plurality of areas and extract discrete space frequency components in respective ones of the arrays or areas, but this method does not enable a plurality of space frequency components to be extracted from the same optical image and also suffers from a disadvantage that it requires a number of photoelectric elements.